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Motion PerceptionDT2350 Human Perception for Information
Technology
Giampiero Salvi
KTH/CSC/TMH [email protected]
HT 2016
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Literature
Goldstein, E. (2009/2014) Sensation andPerception
I Chapter 8: Motion Perception
Weinschenk, S.M. (2011) 100 Things EveryDesigner Needs to Know About People
I surprisingly I could not find any relevantchapter
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Motion Perception
1. stationary observer, moving stimuli
2. moving observer3 / 44
Importance of Motion Perception
I detect danger
I perceive behaviour
I disambiguate vision
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Motion AgnosiaExample: 43-years-old woman who suffered a stroke
Zihl et al. (1983,1991)
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Motion as Attention Capture
The three “F”s
1. Fight
2. Flee
3. Freeze
3. makes it harder to differentiate between theanimal and the background
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Explanation
I bird hard to see because same lines asbackground
I movement perceptually organises bird lines intoone object
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Important Even Without Camouflage
I vision is ambiguous
I pattern recognition more difficult thanmovement detection
I research show we perceive shapes moreaccurately if the object is moving
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Real vs Illusory Motion
Illusory motion:
I apparent motion
I induced motion
I motion aftereffects
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Apparent Motion
It is the basis for movies and television
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Induced Motion
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Motion Aftereffects
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Are Real and Apparent Motion DifferentPerceptually?
Visual cortexLarsen et al. (2006)
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Neural Explanation of Motion PerceptionReichardt detector
Werner Richardt (1969)
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Reichardt detector (1969)
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Reichardt detector (1969)
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Reichardt detector (1969)
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Reichardt detector (1969)
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Reichardt detector (1969)
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Motion Perception Cannot Be Explainedwith the Retina
Jeremy walks, Maria looks straight at the window
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Motion Perception Cannot Be Explainedwith the Retina
Jeremy walks, Maria follows him with the eyes
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Motion Perception Cannot Be Explainedwith the Retina
Maria walks in the room
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Information In The Environment
Gibson: disregard the retina
I Jeremy generates a local disturbance of theoptic array
I this happens both if Maria looks straight orfollows him
I when Maria moves it is different: global opticflow
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Global Optic Flow
I in this case everything moves
I this tells Maria that what she sees is stationaryand that she is the one moving
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Problems
I Eye motions: Corollary discharge theory
I Aperture problem (neuron receptive field)
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Taking Eye Motions Into Account
NOTE: the book does not take head movementsinto account
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Corollary Discharge Model
I corollary discharge signal (CDS)
I image displacement signal (IDS)
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CDM: Moving Person
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CDM: Scanning Stationary Scene
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Behavioural Demonstration 1
corollary discharge (eye movement) without imagedisplacement
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Behavioural Demonstration 2corollary discharge (muscle contraction) withoutimage displacement
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Physiological Evidence
I patient with lesions
I did not receive corollary discharge
I everything moved around when he moved hiseyes
Haarmeier et al. (1997)
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Physiological Evidence in Monkeys
“real motion neuron”
Galletti and Fattori (2003)
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Motion of Arrays of Dots
I possible to vary difficulty of perception (degreeof coherence)
I monkeys’ ability to detect direction
I response of neuron in Medial Temporal cortex
Newsome et al. (1989)
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Relationship to Physiology
(Monkeys must be trained for months to indicatethe direction)
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Effect of Lesioning and Microstimulation
I without lesioning they detect motion with1-2% coherence
I with lesioning they need 10-20% coherence
I with stimulation can change direction ofmovement
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Physiology: The Aperture Problem
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Physiology: The Aperture Problem
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Physiology: The Aperture Problem
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Medial Temporal Area: Pooling Responses
Neurons in Medial Temporal Area
I up to 70msec orientation of the bar
I after 140msec real movement
I use object edge detectors in Striate Cortex
Pack and Born (2001)
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Perceiving Biological MotionPoint-light walker
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Brain Activation to Biological MotionStimulating Superior Temporal Sulcus (STS)disrupts biological motion perception
Grossman et al. (2005)41 / 44
Beyond the Stimulus: Implied MotionKnowledge based motion perceptionrepresentational momentum (Reed and Vinson, 1996)
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Implied and Apparent Motion
Ramachandran and Anstis (1986)
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